Add --fold-sequences operation to swift-parser-test

Use the `SwiftOperators` library to add support for sequence folding
into `swift-parser-test`. Each of the subcommands now supports the
`--fold-sequences` operation, which applies sequence folding using the
standard library operators and any additional precedence groups and
operators defines within the provided source file. The resulting
behavior for each of the subcommands is:

* `verify-round-trip`: ensure that, after folding, the resulting tree
still reproduces the input source.
* `print-diags`: also prints any diagnostics from sequence folding,
e.g., a ** b ** c where ** is non-associative will produce an error.
* `dump-tree`: prints the folded tree, which (for example) will no
longer have any SequenceExprSyntax nodes.
* `reduce`: passes `--fold-sequences` down for reduction.

Author: DougGregor

Package.swift

@@ -126,7 +126,9 @@ let package = Package(
     ),
     .executableTarget(
       name: "swift-parser-test",
-      dependencies: ["SwiftDiagnostics", "SwiftSyntax", "SwiftParser", .product(name: "ArgumentParser", package: "swift-argument-parser")]
+      dependencies: ["SwiftDiagnostics", "SwiftSyntax", "SwiftParser",
+                     "SwiftOperators",
+                     .product(name: "ArgumentParser", package: "swift-argument-parser")]
     ),
     .executableTarget(
         name: "generate-swift-syntax-builder",
@@ -173,7 +175,8 @@ let package = Package(
     ),
     .testTarget(
       name: "SwiftParserTest",
-      dependencies: ["SwiftDiagnostics", "SwiftParser", "_SwiftSyntaxTestSupport"]
+      dependencies: ["SwiftDiagnostics", "SwiftOperators", "SwiftParser",
+                     "_SwiftSyntaxTestSupport"]
     ),
     .testTarget(
       name: "SwiftOperatorsTest",

Sources/swift-parser-test/swift-parser-test.swift

@@ -14,6 +14,7 @@
 import SwiftDiagnostics
 import SwiftSyntax
 import SwiftParser
+import SwiftOperators
 import Foundation
 import ArgumentParser
 #if os(Windows)
@@ -64,6 +65,19 @@ class SwiftParserTest: ParsableCommand {
   )
 }
 
+/// Fold all of the sequences in the given source file.
+func foldAllSequences(_ tree: SourceFileSyntax) -> (Syntax, [Diagnostic]) {
+  var diags: [Diagnostic] = []
+
+  let recordOperatorError: (OperatorError) -> Void = { error in
+    diags.append(error.asDiagnostic)
+  }
+  var operatorTable = OperatorTable.standardOperators
+  operatorTable.addSourceFile(tree, errorHandler: recordOperatorError)
+  let resultTree = operatorTable.foldAll(tree, errorHandler: recordOperatorError)
+  return (Syntax(resultTree), diags)
+}
+
 class VerifyRoundTrip: ParsableCommand {
   required init() {}
 
@@ -82,6 +96,10 @@ class VerifyRoundTrip: ParsableCommand {
   @Option(name: .long, help: "Enable or disable the use of forward slash regular-expression literal syntax")
   var enableBareSlashRegex: Bool?
 
+  @Flag(name: .long,
+          help: "Perform sequence folding with the standard operators")
+  var foldSequences: Bool = false
+
   enum Error: Swift.Error, CustomStringConvertible {
     case roundTripFailed
 
@@ -96,16 +114,24 @@ class VerifyRoundTrip: ParsableCommand {
   func run() throws {
     let source = try getContentsOfSourceFile(at: sourceFile)
 
-    try Self.run(source: source, swiftVersion: swiftVersion, enableBareSlashRegex: enableBareSlashRegex)
+    try Self.run(source: source, swiftVersion: swiftVersion, enableBareSlashRegex: enableBareSlashRegex, foldSequences: foldSequences)
   }
 
-  static func run(source: String, swiftVersion: String?, enableBareSlashRegex: Bool?) throws {
+  static func run(source: String, swiftVersion: String?, enableBareSlashRegex: Bool?, foldSequences: Bool) throws {
     let tree = try Parser.parse(
       source: source,
       languageVersion: swiftVersion,
       enableBareSlashRegexLiteral: enableBareSlashRegex
     )
-    if tree.description != source {
+
+    let resultTree: Syntax
+    if foldSequences {
+      resultTree = foldAllSequences(tree).0
+    } else {
+      resultTree = Syntax(tree)
+    }
+
+    if resultTree.description != source {
       throw Error.roundTripFailed
     }
   }
@@ -123,6 +149,10 @@ class PrintDiags: ParsableCommand {
   @Option(name: .long, help: "Enable or disable the use of forward slash regular-expression literal syntax")
   var enableBareSlashRegex: Bool?
 
+  @Flag(name: .long,
+          help: "Perform sequence folding with the standard operators")
+  var foldSequences: Bool = false
+
   func run() throws {
     let source = try getContentsOfSourceFile(at: sourceFile)
 
@@ -131,7 +161,12 @@ class PrintDiags: ParsableCommand {
       languageVersion: swiftVersion,
       enableBareSlashRegexLiteral: enableBareSlashRegex
     )
-    let diags = ParseDiagnosticsGenerator.diagnostics(for: tree)
+    var diags = ParseDiagnosticsGenerator.diagnostics(for: tree)
+
+    if foldSequences {
+      diags += foldAllSequences(tree).1
+    }
+
     if diags.isEmpty {
       print("No diagnostics produced")
     }
@@ -153,6 +188,10 @@ class DumpTree: ParsableCommand {
   @Option(name: .long, help: "Enable or disable the use of forward slash regular-expression literal syntax")
   var enableBareSlashRegex: Bool?
 
+  @Flag(name: .long,
+          help: "Perform sequence folding with the standard operators")
+  var foldSequences: Bool = false
+
   func run() throws {
     let source = try getContentsOfSourceFile(at: sourceFile)
 
@@ -161,7 +200,14 @@ class DumpTree: ParsableCommand {
       languageVersion: swiftVersion,
       enableBareSlashRegexLiteral: enableBareSlashRegex
     )
-    print(tree.recursiveDescription)
+
+    let resultTree: Syntax
+    if foldSequences {
+      resultTree = foldAllSequences(tree).0
+    } else {
+      resultTree = Syntax(tree)
+    }
+    print(resultTree.recursiveDescription)
   }
 }
 
@@ -177,6 +223,10 @@ class Reduce: ParsableCommand {
   @Option(name: .long, help: "Enable or disable the use of forward slash regular-expression literal syntax")
   var enableBareSlashRegex: Bool?
 
+  @Flag(name: .long,
+          help: "Perform sequence folding with the standard operators")
+  var foldSequences: Bool = false
+
   @Flag(help: "Print status updates while reducing the test case")
   var verbose: Bool = false
 
@@ -221,6 +271,10 @@ class Reduce: ParsableCommand {
           "--swift-version", swiftVersion
         ]
       }
+      if foldSequences {
+        process.arguments! += [ "--fold-sequences" ]
+      }
+
       let sema = DispatchSemaphore(value: 0)
       process.standardOutput = FileHandle.nullDevice
       process.standardError = FileHandle.nullDevice
@@ -252,7 +306,8 @@ class Reduce: ParsableCommand {
   /// Returns `true` if `source` round-tripped successfully, `false` otherwise.
   private func runVerifyRoundTripInCurrentProcess(source: String) throws -> Bool {
     do {
-      try VerifyRoundTrip.run(source: source, swiftVersion: self.swiftVersion, enableBareSlashRegex: self.enableBareSlashRegex)
+      try VerifyRoundTrip.run(source: source, swiftVersion: self.swiftVersion, enableBareSlashRegex: self.enableBareSlashRegex,
+          foldSequences: self.foldSequences)
     } catch {
       return false
     }